The D7100 has taken the only road left to sensor manufacturers until the mad scientists in the labs concoct some new sensing paradigm that is manufacturable: high resolution. If you keep the noise per unit area the same or nearly so, and the well capacity the same or nearly so (as the manufacturers have), the result is a file that can be processed into something far better than the raw per-pixel noise performance would suggest. The penalty you pay is that you have to postprocess the file, or hope that the in-camera processing has been kicked up a notch.

It is well known that with a given sensor technolgoy the way to more dynamic range is a larger photo respeptor well to gather more photons. So there is not another road, which is to increase the photosite well size. This can be achieved with current technology by decreasing the number pixels on a given size sensor, allowing a larger well size.- Jon

Only to the extent that:

1) lithography compromises well areal fill ratio, since sensor noise and dynamic range both scale by area (depth is constrained by epitaxial processing)

At the current level of technology, these sources are relatively small contributors; further tricks, such as BSI (wiring on the backside), will not result in dramatic gains. At best they'll nibble at the edges.

The D600 outperforms the D800 at the pixel level by only a small margin. The NEX-5 outperforms the NEX-7 by a similar small margin. But at the same image resolution, their performance is essentially identical.

To realize the 2 stop performance gains similar to that seen from the D80 to D90 transition, we will have to change bulk technology throughout the sensing chain - losing the Bayer CFA, etc.. And then we're up against the fundamental limit of photon noise.